Amazon's slowdown of their business with Hachette Book Group as the parties battle over terms took another turn Thursday evening, as site visitors noted on social media the disappearance of pre-order buying capability for print and Kindle editions of many forthcoming HBG titles. Among affected titles due for publication in June are JK Rowling's next Robert Galbraith novel SILKWORM; Michael Koryta's THOSE WHO WISH ME DEAD; Megan Abbott's THE FEVER; Elin Hilderbrand's THE MATCHMAKER, and Tom Rob Smith's THE FARM, plus Anne Rivers Siddons' THE GIRLS OF AUGUST (due in early July). The affected books now display as "currently unavailable" and offer to have customers "sign up to be notified when this item becomes available" -- as those same titles are readily available for pre-order at other online booksellers. Additionally, some affected books do not have any Kindle page at all.

Following our original report Thursday, Hachette Book Group ceo Michael Pietsch sent an email to authors on Friday morning, obtained by PL. Pietsch confirms, "I am sorry to tell you that Amazon has now taken preorder capabilities away from Hachette Book Group publications" and adds: "Please know that we are doing everything in our power to find a solution to this difficult situation, one that best serves our authors and their work, and that preserves our ability to survive and thrive as a strong and author-centric publishing company." He acknowledges: "I know this is not a comfortable situation for most of you, and I appreciate your support and the many messages I’ve received."

The move is significant as an overt extension of the current standoff between Amazon and HBG. Slowing down the supply chain of physical books and tweaking of discount policies still left HBG titles available for order, even if the conditions changed; removing pre-order capability, while not the same as a full buy-button removal, is still a direct cessation of one form of sale of HBG books.

Amazon has also made it difficult to search for these upcoming titles as well. For example, inputting "Tom Rob Smith The Farm" does not immediately pull up the hardcover or Kindle editions of the book, but does yield as the top option a "free preview -- first 25 pages" that Grand Central made available on April 15. Elin Hilderbrand fans are also directed to a "free preview" ebook instead of the actual forthcoming book.

Improbably, two Hachette titles still hold places on Amazon's own list of top 25 pre-orders -- even though you can no longer actually pre-order them: Douglas Preston and Lincoln Child's August release THE LOST ISLAND was still the No. 7 pre-order this morning, while the next Galbraith was listed as No. 15.

Looking further ahead on the calendar, the hardcover edition of Carlos Santana's autobiography can still be pre-ordered, but the Kindle edition is unavailable; the same goes for Edith Pearlman's forthcoming short story collection HONEYDEW, slated for a January 2015 release date. Buy buttons have also been removed for James Patterson's forthcoming titles; Paolo Bacigalupi's THE DOUBT FACTORY (October); Gail Carriger's YA novel (November); a collection of short stories and novellas, THE MARTINI SHOT, by George Pelecanos (January); and Chuck Todd's THE STRANGER (November).

Customers who pre-ordered any of these and other forthcoming Hachette titles before May 22 should expect to see their orders honored. A spokesperson for Amazon declined to comment on Thursday night.